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The 2003 Yarragadee Moblas 5 local tie survey

Abstract

The combination of Space Geodetic techniques is fundamental to the definition of the International Terrestrial Reference Frame
(ITRF). An integral component of this combination is the accurately measured and expressed connection between the different
space geodetic techniques, commonly referred to as the local tie. Our ambition is to observe each local tie at an accuracy
level of 1-2 mm.
The Yarragadee (Moblas 5) Satellite Laser Ranging (SLR) observatory, located in Western Australia, is co-located with permanent
GPS, DORIS and GLONASS systems. A local tie survey at Yarragadee was completed over four days, the 24th to 27th November
2003, by specialist Geoscience Australia geodetic surveyors using precision classical geodetic observations and geodetic GPS
observations. The purpose of this survey was to repeat the determination of the relationship between each of the observing
techniques to the surrounding survey control. This survey also connected the new DORIS antenna position, YASB 50107S011,
into the existing control, along with its pillar reference point, YASM 50107M007. This type of local tie survey has previously
been undertaken at Yarragadee in 1992, 1999 and 2001.
The 2003 survey results are compared with those observed at Yarragadee in 1999 and 2001. The results indicate a significant
movement vertically, 4 to 5 mm, at RM3 and YAR2 50107M004 between the 1999 survey and the 2003 survey. The motion is not
present to the same extent between the 2001 and 2003 surveys, indicating the displacement took place between the 1999 and
2001 surveys.